Today I bought two glass tops from petco for my 55. When got home I realized one was cracked and the other seems too short. It doesn't fit in the area for the top. I can get it to sit above it, but it takes a long.time to get it centered. Should I return both? Also I'm confused on how to program my timer. The fixture I bought comes on as soon as you plug it in.

With regards to the glass top, If it was damaged in the box when you bought it then yes take it back. If it was something you did well it is up to you as to wether or not to take it back and try and get a replacement.
If you do not keep fish which are really known jumpers then you can always leave the tank open topped, just adds a bit to evaporation.

The timer could be that you have to pull the tabs up to shut it off and down for on, I had that issue with my timers for my saltwater tank.

No as I am in Canada and they dont ship here. I have Hagen tanks and it is very easy to get Hagen tops here.

The products they sell though are very good from what I hear on other forums and on here.

Hopefully they'll fit. I'll try to post a pic. On a funny note, I went to my Lfs and when buying for plants this is what happened: Worker: what can I get for you. Me: yes, Umm can I one of those crypts, two of the cabomba and that b)razilian penny wort Worker: You want WHAT? Me: (points to it) the brazilian penny wort. Worker: (Points to it) THIS??. Me ...yes...? Worker: Hay men this guy says this stuff is... what did you call it?? Me: ....brazilian penny wort?? Other guy REALLY??!!... we've been trying to figure out what it was all week. Worker: Call maggie and ask how much it is. other guy: Ok. My sister and I found this VERY funny. Here I am a 14 YEAR OLD and I know more than the store workers.... WOW